1) Field of the Invention
This invention relates to a water swellable resin composition, and more specifically to a water swellable resin composition useful as sealing compounds, waterproofing agents, water-holding agents, dew-preventing agents, water-penetration preventing materials, sweat-absorbing materials, sanitary napkins, etc.
2) Description of the Prior Art
As water swellable resins known to date, there are, for example, crosslinked products of water-soluble resins, resins formed by graft-polymerizing a water-soluble monomer on starch or the like, and block copolymers composed of a hydrophilic resin and a hydrophobic resin.
The crosslinked products of the water-soluble resins involve the problem that when they have a low crosslinking degree, excreted portion into water increases although they exhibit high swellability and when they have a high crosslinking degree, their swellability is reduced although they are not dissolved into water. High swellability and water insolubility are thus contradictory. They are used as dispersions in an organic solvent, because it is difficult to use them alone. They however have low compatibility with organic solvents, so that various problems exist.
The grafted products use a natural material as a base material. They are hence accompanied by the drawback that they are biodegradable and have poor long-term stability in a wet state. They also involve the problem that their compatibility with organic solvents is low.
On the other hand, the water swellable resins of the block copolymer type are excellent in swellability, wet stability, compatibility with organic solvents, etc. Their production processes are however trouble-some, leading to the drawback that their application fields are limited.